MAPT and Alzheimer disease: AD is a chronic neurodegenerative disease characterized by progressive cognitive and memory deficits, as characterized by massive death and loss of central cholinergic neurons, hyperphosphorylation of Tau proteins to form neurofibrillary tangles and deposition of β-amyloid (Aβ), which leads to damage to cholinergic nerve cells, decreased levels of choline acetyltransferase (ChAT) and decreased acetylcholine transmitter synthesis is reduced (Busche and Hyman, 2020).